Dr. F. Miiller on Philomedusa Vogtii. 435 
on the hinder part of the body, alternating with the longitudinal 
furrows. Their number increases with age, and rises, in the 
largest specimens, to about twenty in each row. Their diameter 
varies: the largest orifice that I have met with was 0-1 millim. 
in length, and half that breadth. Under the microscope, the 
minute particles driven about by the cilia of the body-cavity 
may sometimes be seen to issue from them. They are of course 
closed by the contraction of the wall of the body, but are also 
capable of contracting and closing independently: when con- 
tracting, they appear to be surrounded by a pale space; and 
when closed, a pale spot appears in their place. 
The middle of the posterior extremity is completely closed in 
the animal when filled with water; but on rapid contraction, a 
wide orifice for the escape of the water opens at this point*, 
through which portions of the mesenteric frills not unfrequently 
pass at the same time. In a large specimen which I put into a 
test-tube in order to observe it more conveniently, I saw, after 
it had distended itself again with water, a slender cord stretched 
tightly from the end of one of the longer mesenteric frills to the 
middle of the posterior extremity, which, as I knew, was not 
there before. After a fresh slight contraction of the animal, 
caused by shaking the glass, the cord began to remove from the 
posterior extremity, and contracted itself with extraordinary 
slowness, still retaining its straight form: thus it proved itself 
to be a fragment of the mesenteric frill in question, which had 
been fixed during the first contraction, and set free by the open- 
ing of the terminal orifice caused by the second contraction. 
I first found Philomedusa Vogtii adhering singly to the lower 
surface of the disk in Olindias (nov. gen. Eucopidarum), and 
subsequently in plenty upon Chrysaora, in which it dwells on the 
arms, in the sexual cavities, and in the stomach and its sacs. 
From a single Medusa of the last-named genus I have removed 
more than twenty of these Polypes. The animals taken from 
the Medusz usually have fragments of the tentacular filaments, 
genitalia, stomachal filaments, &c., of the host in their stomachs ; 
and urticating capsules of the Medusa are often met with in the 
body-cavity of the Polype. Like the Actiniz, they bear captivity 
well; they will do without food for months, and will also take 
other food besides parts of Meduse, exhibiting a preference 
for Annelides. If a large number be kept in the same vessel, 
* This is also the case in Cerianthus (Jules Haime, in Ann. des Se. Nat. 
sér. 4. tome i. p. 341), with which polype that above described has much 
affinity. The number and especially the position of the tentacles certainly 
does not agree, as Cerianthus possesses a double and Philomedusa a single 
row of tentacles. However, with regard to their systematic position, it 
must be borne in mind that the animals, as above stated, have not yet been 
observed in a state of sexual maturity (Max Schultze). 
